Prior to granting approval for proposed construction or development, government authorities are requiring more comprehensive studies on their potential impact on the natural environment. Consequently, the measurement of the effects of human intervention on the natural environment, particularly on populations of rare or endangered species of animals and on the diversity of animal species, is an important requirement.
Currently used wildlife monitoring schemes typically involve experienced terrestrial biologists or surveyors entering the environment to be monitored and making first hand auditory and visual inspections of the terrestrial environment. These manual inspections may be unsatisfactory for several reasons. First, manual inspections are labour intensive, may require large numbers of individuals in order to cover a sufficiently representative territory of the environment, and may therefore be very difficult to perform; if sufficient resources are not available the results obtained may not be reliable.
Second, manual inspections may require lengthy periods of time to complete. Typically, the environments to be monitored are remote from city centres and, the travelling time to and from the site may be substantial. At the site, surveyors must approach the environment with great care in order to avoid disrupting the terrestrial environment.
Third, manual inspections are limited in their scope, because they are usually restricted to daylight hours and, as a result, nocturnal species are not generally observed. Animals may also be visually obscured by forest vegetation, and some environments such as swamps and marshes may not be easily accessible.
Finally, the integrity of any measured data is subject to uncertainty and error due to the highly subjective nature of auditory and visual observations.
Automatic monitoring systems have been developed in order to perform the monitoring function of surveyors. These systems have typically used conventional analog recorders to collect the animal vocalizations, or calls, from a representative area. However, recorders for recording long term terrestrial data (beyond 12 hours) at multiple sites and having a wide bandwidth (up to 10 kHz) are relatively expensive. Furthermore, the analysis of the recordings has to be conducted by surveyors out of the field, which involves labour intensive analysis by biologists who are deprived of the benefit of being present in the physical environment when identifying the call.
The present invention overcomes the drawbacks associated with manual inspections by providing an automated system which permits the continuous recording of animal vocalizations with a minimum of disturbance to the terrestrial environment. The present invention also permits the monitoring of a significant area with minimum labour requirements, and reduces misidentification resulting from observer biases.
In order that the invention may be readily understood, preferred embodiments thereof will now be described, by way of example, with reference to the accompanying drawings.